1 /* vi: set sw=4 ts=4: */
4 * Bjorn Wesen, Axis Communications AB (bjornw@axis.com)
6 * Licensed under GPL, see file LICENSE in this tarball for details.
8 * ---------------------------------------------------------------------------
9 * (C) Copyright 2000, Axis Communications AB, LUND, SWEDEN
10 ****************************************************************************
12 * The telnetd manpage says it all:
14 * Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for
15 * a client, then creating a login process which has the slave side of the
16 * pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the
17 * master side of the pseudo-terminal, implementing the telnet protocol and
18 * passing characters between the remote client and the login process.
20 * Vladimir Oleynik <dzo@simtreas.ru> 2001
21 * Set process group corrections, initial busybox port
27 #include <sys/socket.h>
29 #include <sys/ioctl.h>
34 #include <netinet/in.h>
35 #include <arpa/inet.h>
44 #include <arpa/telnet.h>
46 #include <sys/syslog.h>
52 #ifdef CONFIG_FEATURE_IPV6
53 #define SOCKET_TYPE AF_INET6
54 typedef struct sockaddr_in6 sockaddr_type;
56 #define SOCKET_TYPE AF_INET
57 typedef struct sockaddr_in sockaddr_type;
62 static const char *loginpath = "/bin/login";
64 static const char *loginpath;
66 static const char *issuefile = "/etc/issue.net";
68 /* shell name and arguments */
70 static const char *argv_init[] = {NULL, NULL};
72 /* structure that describes a session */
75 #ifdef CONFIG_FEATURE_TELNETD_INETD
76 int sockfd_read, sockfd_write, ptyfd;
77 #else /* CONFIG_FEATURE_TELNETD_INETD */
78 struct tsession *next;
80 #endif /* CONFIG_FEATURE_TELNETD_INETD */
82 /* two circular buffers */
84 int rdidx1, wridx1, size1;
85 int rdidx2, wridx2, size2;
90 This is how the buffers are used. The arrows indicate the movement
93 +-------+ wridx1++ +------+ rdidx1++ +----------+
94 | | <-------------- | buf1 | <-------------- | |
95 | | size1-- +------+ size1++ | |
97 | | rdidx2++ +------+ wridx2++ | |
98 | | --------------> | buf2 | --------------> | |
99 +-------+ size2++ +------+ size2-- +----------+
101 Each session has got two buffers.
107 static struct tsession *sessions;
112 Remove all IAC's from the buffer pointed to by bf (recieved IACs are ignored
113 and must be removed so as to not be interpreted by the terminal). Make an
114 uninterrupted string of characters fit for the terminal. Do this by packing
115 all characters meant for the terminal sequentially towards the end of bf.
117 Return a pointer to the beginning of the characters meant for the terminal.
118 and make *num_totty the number of characters that should be sent to
121 Note - If an IAC (3 byte quantity) starts before (bf + len) but extends
122 past (bf + len) then that IAC will be left unprocessed and *processed will be
125 FIXME - if we mean to send 0xFF to the terminal then it will be escaped,
126 what is the escape character? We aren't handling that situation here.
128 CR-LF ->'s CR mapping is also done here, for convenience
132 remove_iacs(struct tsession *ts, int *pnum_totty) {
133 unsigned char *ptr0 = (unsigned char *)ts->buf1 + ts->wridx1;
134 unsigned char *ptr = ptr0;
135 unsigned char *totty = ptr;
136 unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1);
144 /* We now map \r\n ==> \r for pragmatic reasons.
145 * Many client implementations send \r\n when
146 * the user hits the CarriageReturn key.
148 if (c == '\r' && (*ptr == '\n' || *ptr == 0) && ptr < end)
153 * TELOPT_NAWS support!
155 if ((ptr+2) >= end) {
156 /* only the beginning of the IAC is in the
157 buffer we were asked to process, we can't
158 process this char. */
163 * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE
165 else if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) {
168 break; /* incomplete, can't process */
169 ws.ws_col = (ptr[3] << 8) | ptr[4];
170 ws.ws_row = (ptr[5] << 8) | ptr[6];
171 (void) ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
175 /* skip 3-byte IAC non-SB cmd */
177 fprintf(stderr, "Ignoring IAC %s,%s\n",
178 TELCMD(*(ptr+1)), TELOPT(*(ptr+2)));
185 processed = ptr - ptr0;
186 num_totty = totty - ptr0;
187 /* the difference between processed and num_to tty
188 is all the iacs we removed from the stream.
189 Adjust buf1 accordingly. */
190 ts->wridx1 += processed - num_totty;
191 ts->size1 -= processed - num_totty;
192 *pnum_totty = num_totty;
193 /* move the chars meant for the terminal towards the end of the
195 return memmove(ptr - num_totty, ptr0, num_totty);
203 #ifdef CONFIG_FEATURE_DEVPTS
204 p = open("/dev/ptmx", 2);
208 strcpy(line, ptsname(p));
216 strcpy(line, "/dev/ptyXX");
218 for (i = 0; i < 16; i++) {
219 line[8] = "pqrstuvwxyzabcde"[i];
221 if (stat(line, &stb) < 0) {
224 for (j = 0; j < 16; j++) {
225 line[9] = j < 10 ? j + '0' : j - 10 + 'a';
227 fprintf(stderr, "Trying to open device: %s\n", line);
229 if ((p = open(line, O_RDWR | O_NOCTTY)) >= 0) {
235 #endif /* CONFIG_FEATURE_DEVPTS */
241 send_iac(struct tsession *ts, unsigned char command, int option)
243 /* We rely on that there is space in the buffer for now. */
244 char *b = ts->buf2 + ts->rdidx2;
253 static struct tsession *
254 #ifdef CONFIG_FEATURE_TELNETD_INETD
255 make_new_session(void)
256 #else /* CONFIG_FEATURE_TELNETD_INETD */
257 make_new_session(int sockfd)
258 #endif /* CONFIG_FEATURE_TELNETD_INETD */
260 struct termios termbuf;
263 struct tsession *ts = malloc(sizeof(struct tsession) + BUFSIZE * 2);
265 ts->buf1 = (char *)(&ts[1]);
266 ts->buf2 = ts->buf1 + BUFSIZE;
268 #ifdef CONFIG_FEATURE_TELNETD_INETD
270 ts->sockfd_write = 1;
271 #else /* CONFIG_FEATURE_TELNETD_INETD */
273 #endif /* CONFIG_FEATURE_TELNETD_INETD */
275 ts->rdidx1 = ts->wridx1 = ts->size1 = 0;
276 ts->rdidx2 = ts->wridx2 = ts->size2 = 0;
278 /* Got a new connection, set up a tty and spawn a shell. */
280 pty = getpty(tty_name);
283 syslog(LOG_ERR, "All terminals in use!");
292 /* Make the telnet client understand we will echo characters so it
293 * should not do it locally. We don't tell the client to run linemode,
294 * because we want to handle line editing and tab completion and other
295 * stuff that requires char-by-char support.
298 send_iac(ts, DO, TELOPT_ECHO);
299 send_iac(ts, DO, TELOPT_NAWS);
300 send_iac(ts, DO, TELOPT_LFLOW);
301 send_iac(ts, WILL, TELOPT_ECHO);
302 send_iac(ts, WILL, TELOPT_SGA);
304 if ((pid = fork()) < 0) {
305 syslog(LOG_ERR, "Could not fork");
308 /* In child, open the child's side of the tty. */
311 for(i = 0; i <= maxfd; i++)
313 /* make new process group */
316 if (open(tty_name, O_RDWR /*| O_NOCTTY*/) < 0) {
317 syslog(LOG_ERR, "Could not open tty");
323 tcsetpgrp(0, getpid());
325 /* The pseudo-terminal allocated to the client is configured to operate in
326 * cooked mode, and with XTABS CRMOD enabled (see tty(4)).
329 tcgetattr(0, &termbuf);
330 termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */
331 termbuf.c_oflag |= ONLCR|XTABS;
332 termbuf.c_iflag |= ICRNL;
333 termbuf.c_iflag &= ~IXOFF;
334 /*termbuf.c_lflag &= ~ICANON;*/
335 tcsetattr(0, TCSANOW, &termbuf);
337 print_login_issue(issuefile, NULL);
339 /* exec shell, with correct argv and env */
340 execv(loginpath, (char *const *)argv_init);
343 syslog(LOG_ERR, "execv error");
352 #ifndef CONFIG_FEATURE_TELNETD_INETD
354 free_session(struct tsession *ts)
356 struct tsession *t = sessions;
358 /* Unlink this telnet session from the session list. */
367 kill(ts->shell_pid, SIGKILL);
369 wait4(ts->shell_pid, NULL, 0, NULL);
374 if (ts->ptyfd == maxfd || ts->sockfd == maxfd)
376 if (ts->ptyfd == maxfd || ts->sockfd == maxfd)
381 #endif /* CONFIG_FEATURE_TELNETD_INETD */
384 telnetd_main(int argc, char **argv)
386 #ifndef CONFIG_FEATURE_TELNETD_INETD
389 #endif /* CONFIG_FEATURE_TELNETD_INETD */
390 fd_set rdfdset, wrfdset;
392 #ifndef CONFIG_FEATURE_TELNETD_INETD
395 struct in_addr bind_addr = { .s_addr = 0x0 };
396 #endif /* CONFIG_FEATURE_TELNETD_INETD */
398 static const char options[] =
399 #ifdef CONFIG_FEATURE_TELNETD_INETD
401 #else /* CONFIG_EATURE_TELNETD_INETD */
403 #endif /* CONFIG_FEATURE_TELNETD_INETD */
407 loginpath = DEFAULT_SHELL;
411 c = getopt( argc, argv, options);
420 #ifndef CONFIG_FEATURE_TELNETD_INETD
422 portnbr = atoi(optarg);
425 if (inet_aton(optarg, &bind_addr) == 0)
428 #endif /* CONFIG_FEATURE_TELNETD_INETD */
434 if (access(loginpath, X_OK) < 0) {
435 bb_error_msg_and_die ("'%s' unavailable.", loginpath);
438 argv_init[0] = loginpath;
440 openlog(bb_applet_name, 0, LOG_USER);
442 #ifdef CONFIG_FEATURE_TELNETD_INETD
444 sessions = make_new_session();
445 #else /* CONFIG_EATURE_TELNETD_INETD */
448 /* Grab a TCP socket. */
450 master_fd = bb_xsocket(SOCKET_TYPE, SOCK_STREAM, 0);
451 (void)setsockopt(master_fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
453 /* Set it to listen to specified port. */
455 memset((void *)&sa, 0, sizeof(sa));
456 #ifdef CONFIG_FEATURE_IPV6
457 sa.sin6_family = AF_INET6;
458 sa.sin6_port = htons(portnbr);
459 /* sa.sin6_addr = bind_addr6; */
461 sa.sin_family = AF_INET;
462 sa.sin_port = htons(portnbr);
463 sa.sin_addr = bind_addr;
466 bb_xbind(master_fd, (struct sockaddr *) &sa, sizeof(sa));
467 bb_xlisten(master_fd, 1);
471 #endif /* CONFIG_FEATURE_TELNETD_INETD */
479 /* select on the master socket, all telnet sockets and their
480 * ptys if there is room in their respective session buffers.
483 #ifndef CONFIG_FEATURE_TELNETD_INETD
484 FD_SET(master_fd, &rdfdset);
485 #endif /* CONFIG_FEATURE_TELNETD_INETD */
488 #ifndef CONFIG_FEATURE_TELNETD_INETD
490 #endif /* CONFIG_FEATURE_TELNETD_INETD */
491 /* buf1 is used from socket to pty
492 * buf2 is used from pty to socket
495 FD_SET(ts->ptyfd, &wrfdset); /* can write to pty */
497 if (ts->size1 < BUFSIZE) {
498 #ifdef CONFIG_FEATURE_TELNETD_INETD
499 FD_SET(ts->sockfd_read, &rdfdset); /* can read from socket */
500 #else /* CONFIG_FEATURE_TELNETD_INETD */
501 FD_SET(ts->sockfd, &rdfdset); /* can read from socket */
502 #endif /* CONFIG_FEATURE_TELNETD_INETD */
505 #ifdef CONFIG_FEATURE_TELNETD_INETD
506 FD_SET(ts->sockfd_write, &wrfdset); /* can write to socket */
507 #else /* CONFIG_FEATURE_TELNETD_INETD */
508 FD_SET(ts->sockfd, &wrfdset); /* can write to socket */
509 #endif /* CONFIG_FEATURE_TELNETD_INETD */
511 if (ts->size2 < BUFSIZE) {
512 FD_SET(ts->ptyfd, &rdfdset); /* can read from pty */
514 #ifndef CONFIG_FEATURE_TELNETD_INETD
517 #endif /* CONFIG_FEATURE_TELNETD_INETD */
519 selret = select(maxfd + 1, &rdfdset, &wrfdset, 0, 0);
524 #ifndef CONFIG_FEATURE_TELNETD_INETD
525 /* First check for and accept new sessions. */
526 if (FD_ISSET(master_fd, &rdfdset)) {
531 if ((fd = accept(master_fd, (struct sockaddr *)&sa,
535 /* Create a new session and link it into
537 struct tsession *new_ts = make_new_session(fd);
539 new_ts->next = sessions;
549 /* Then check for data tunneling. */
552 while (ts) { /* For all sessions... */
553 #endif /* CONFIG_FEATURE_TELNETD_INETD */
554 #ifndef CONFIG_FEATURE_TELNETD_INETD
555 struct tsession *next = ts->next; /* in case we free ts. */
556 #endif /* CONFIG_FEATURE_TELNETD_INETD */
558 if (ts->size1 && FD_ISSET(ts->ptyfd, &wrfdset)) {
561 /* Write to pty from buffer 1. */
563 ptr = remove_iacs(ts, &num_totty);
565 w = write(ts->ptyfd, ptr, num_totty);
567 #ifdef CONFIG_FEATURE_TELNETD_INETD
569 #else /* CONFIG_FEATURE_TELNETD_INETD */
573 #endif /* CONFIG_FEATURE_TELNETD_INETD */
577 if (ts->wridx1 == BUFSIZE)
581 #ifdef CONFIG_FEATURE_TELNETD_INETD
582 if (ts->size2 && FD_ISSET(ts->sockfd_write, &wrfdset)) {
583 #else /* CONFIG_FEATURE_TELNETD_INETD */
584 if (ts->size2 && FD_ISSET(ts->sockfd, &wrfdset)) {
585 #endif /* CONFIG_FEATURE_TELNETD_INETD */
586 /* Write to socket from buffer 2. */
587 maxlen = MIN(BUFSIZE - ts->wridx2, ts->size2);
588 #ifdef CONFIG_FEATURE_TELNETD_INETD
589 w = write(ts->sockfd_write, ts->buf2 + ts->wridx2, maxlen);
592 #else /* CONFIG_FEATURE_TELNETD_INETD */
593 w = write(ts->sockfd, ts->buf2 + ts->wridx2, maxlen);
599 #endif /* CONFIG_FEATURE_TELNETD_INETD */
602 if (ts->wridx2 == BUFSIZE)
606 #ifdef CONFIG_FEATURE_TELNETD_INETD
607 if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd_read, &rdfdset)) {
608 #else /* CONFIG_FEATURE_TELNETD_INETD */
609 if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd, &rdfdset)) {
610 #endif /* CONFIG_FEATURE_TELNETD_INETD */
611 /* Read from socket to buffer 1. */
612 maxlen = MIN(BUFSIZE - ts->rdidx1,
613 BUFSIZE - ts->size1);
614 #ifdef CONFIG_FEATURE_TELNETD_INETD
615 r = read(ts->sockfd_read, ts->buf1 + ts->rdidx1, maxlen);
616 if (!r || (r < 0 && errno != EINTR))
618 #else /* CONFIG_FEATURE_TELNETD_INETD */
619 r = read(ts->sockfd, ts->buf1 + ts->rdidx1, maxlen);
620 if (!r || (r < 0 && errno != EINTR)) {
625 #endif /* CONFIG_FEATURE_TELNETD_INETD */
626 if (!*(ts->buf1 + ts->rdidx1 + r - 1)) {
633 if (ts->rdidx1 == BUFSIZE)
637 if (ts->size2 < BUFSIZE && FD_ISSET(ts->ptyfd, &rdfdset)) {
638 /* Read from pty to buffer 2. */
639 maxlen = MIN(BUFSIZE - ts->rdidx2,
640 BUFSIZE - ts->size2);
641 r = read(ts->ptyfd, ts->buf2 + ts->rdidx2, maxlen);
642 if (!r || (r < 0 && errno != EINTR)) {
643 #ifdef CONFIG_FEATURE_TELNETD_INETD
645 #else /* CONFIG_FEATURE_TELNETD_INETD */
649 #endif /* CONFIG_FEATURE_TELNETD_INETD */
653 if (ts->rdidx2 == BUFSIZE)
657 if (ts->size1 == 0) {
661 if (ts->size2 == 0) {
665 #ifndef CONFIG_FEATURE_TELNETD_INETD
668 #endif /* CONFIG_FEATURE_TELNETD_INETD */